This invention relates generally to a printing method and system and, more particularly, to a method and system of performing feed-forward toner consumption estimation to manage replenishment of toners during printing.
Maintaining stable toner concentration levels is important for maintaining image quality in a printing environment. More specifically, dispensing too little toner because of low toner concentration levels may create areas in a printed image that appear faded, while too much toner may saturate a region in a printed image.
In monochrome (i.e., black and white) printing environments, feedback control systems have been used to regulate toner concentration levels during printing in an attempt to maintain acceptable levels of printed image quality. Typically, these feedback control systems use sensors to measure toner concentration levels in small patches developed during inter-document zones. When the feedback indicates that the toner concentrations levels are too low to maintain an acceptable printed image quality, the toner is mixed with a carrier in the mixing sump until a desired mixture and level is reached.
Although these prior systems work, they have had some problems. One of the problems is the limited sampling period during the inter-document zones which does not provide adequate feedback information about toner concentration levels. As a result, toner concentration levels may actually be too low or too high, but the erroneous condition may not be corrected early enough because of the inaccurate detection and feedback. Another problem is the large lag or delay time between recognizing the need to replenish until the time the toner can be replenished to return the toner concentration level to a nominal state. In fact, in high speed printing systems, sole reliance on a feedback sensor and control system has proven to be marginally stable or unstable in maintaining toner concentration at an acceptably narrow range when many high-density images, demanding considerable toner consumption, are printed. As a result, image quality may suffer until the toner can be replenished.
In color xerography, maintaining stable and accurate toner concentration levels may be more imperative for achieving consistent printed image quality. Poor color balance in printed images may result if toner concentration levels are not maintained at appropriate levels during printing. Further, particularly for image-on-image (xe2x80x9cIOIxe2x80x9d) xerographic color printers, but not limited thereto, the adverse effects caused by improper toner concentration levels are compounded by the IOI interactions of different color separations in the printed images.
Thus, in high speed printing environments, for example, a need exists for metering toner in proportion to image density to anticipate toner consumption in real time to avoid the delays and errors noted above. Furthermore, obtaining a reasonably accurate signal for each color separation in a IOI color printer, for example, would require corrections for interactions between color separations.
A method for managing replenishment of toners in accordance with one embodiment of the present invention includes determining a quantity of image units for each of one or more colors in a printed image, adjusting each of the quantity of image units based upon one or more color relationships among the one or more colors, and replenishing one or more of the toners when the adjusted quantity of image units for the one or more of the toners indicates a need for replenishment.
A system for managing replenishment of toners in accordance with the present invention includes a quantizing system, an adjustment system, and a replenishment system. The quantizing system determines a quantity of image units for each of one or more colors in a printed image. The adjustment system adjusts each of the quantity of image units based upon one or more color relationships among the one or more colors. The replenishment system replenishes one or more of the toners when the adjusted quantity of image units for the one or more of the toners indicates a need for replenishment.
The present invention provides a number of advantages, including enabling the accumulation of high-definition contone image data at very high data rates and accounting for and correcting color-image interactions and image-wise occlusions during pixel estimation. In addition, the present invention enables toner concentration levels to be maintained at desired levels during color xerography while improving overall image quality.